Controllable inductor



1962 c. e. SONTHEIMER CONTROLLABLE INDUCTOR Original Filed July 22, 1954k m m RM n PM N R ETNI O V M w n I. A G W mi AB. C

United States Patent ()fiice 3,060,393 Patented Oct. 23, 1962 3,060,393CONTRQLLABLE INDUCTOR Carl G. Sontheinrer, Riverside, Conn, assignor toTrak Electronics Company, inc, a corporation of Connecticut Originalapplication Early 22, 1954, Ser. No. 445,146, new Patent No. 2,973,431,dated Feb. 28, 1961. Divided and this application Oct. 16, 1958, Ser.No. 771,935 6 Claims. (Cl. 336--2tl) The present invention relates tocontrollable inductors including magnetically saturable material and inwhich the effective inductance of a signal winding is controlled byvarying the relative magnetic saturation of the saturable material. Inparticular, this invention relates to controllable inductors includingadjustment mechanism for adjusting their operating characteristics. Thisapplication is a division of application Serial No. 445,146, whichissued as Patent No. 2,973,431.

The various aspects and advantages of the present invention will beapparent from the following description of a controllable inductorincorporating the invention considered in conjunction with theaccompanying drawings, in which:

FIGURE 1 is a perspective view of an adjustable controllable inductorembodying the present invention, the control winding being indicateddiagrammatically; and

FIGURE 2 is an elevational view of the inductor of FIGURE 1.

In FIGURES 1 and 2 an embodiment of a variable inductor 240 is shown.This variable inductor 24% may be used for various inductance controlapplications, for example, it may be used with two other similarcontrollable inductors (not shown) to provide the control circuits in aradio receiver, for example, as shown in US. Patent No. 2,973,431. Thecontrollable inductor 240 has a control winding 37a which in operationis supplied with an electrical current which is controlled so as toprovide the desired inductance control action, for example, the controlwinding 37a may be connected in series with the corresponding controlwindings (not shown) of the other two similar controllable inductors,mentioned above, as will be understood. This inductor 240 includes asignal core portion 42a comprising two elongated bars of ferrite orferromagnetic ceramic placed longitudinally adjacent one another. Thisferrite material may be similar to that disclosed by Snock in US.Patents Nos. 2,452,529; 2,452,530; and 2,452,531. A generally elongatedhexagonal signal winding opening is formed by trapezoidal recesses inthe adjoining sides of the two bars. The signal core portion 42a carriesa signal winding 4811 which is in two halves extending through thehexagonal opening and connected in series, so that their magnetic fieldsare in aiding relationship around the opening to induce flux flowingaround this opening. Core 42a is bridged across between a pair of coppershimes Gila resting against the side legs 2421 and 242-2 of a controlcore portion 52a. The control winding 37a is wound on the back part ofthe core 52a. The core 52a is made of a flexible magnetizable material,for example a strap of soft iron bent into a U shape to form the twoside legs 242 and 243, with the ends of the side legs being bent overagain toward one another in a spaced overlapping relationship to form amagnetic path for the control flux between legs 242 and 243 in shuntwith the path through the core 42a. An adjustment of the effectivereluctance of this shunt path is provided by a large-headed machinescrew 244 of non-magnetic material threaded through a hole in the outerend of the leg 242 and resting against the inner end of the leg 243. Bytightening it, this shunt reluctance is increased, so that for any givenvalue of the current in the control winding 37a the degree of magneticsaturation of the signal core portion 42a is increased lowering theeffective inductance of the winding 48a thereon. In overall effecttightening the screw 244 is equivalent to adding some turns in thewinding 37a.

When the three inductors similar to inductor 240 have their controlwindings connected in series there may be deviations of the controlledinductance values in the respective circuits being controlled thereby,so that due to individual differences they do not track properly. Theshunt control flux path adjustment by the screw 244 enablescompensations to be made for the individual deviations so that theinductance values are caused to track one another.

Another adjustment for tracking characteristics is provided by changingthe reluctance in series with the control flux path through the core 42awith a non-magnetic machine screw 248 which serves to skew the rightshim 60a to change the effective length of the reluctance region betweenthe right end of the core 42a and the leg 243. To facilitate the tilting.of this shim, the end of the screw may be rounded to fit it into asocket in the shim. By adjusting the screws 244 and 248 all of thecontrollable inductors 244i used can be adjusted to track one another asdesired.

Among the advantages of using separate controllable inductors instead ofhaving them ganged upon a single control yoke is that each of them maythen be located closely adjacent the portion of the receiver circuitdesired, thus advantageously enabling the use of shorter interconnectingwires within the receiver.

The advantage of such arrangements will be understood both from thestandpoint of convenience and utility as well as from the standpoint ofease of service and maintenance.

From the foregoing description it will be understood that the presentinvention provides an adjustable controllable inductor having manyadvantages as discussed above, and it is understood that the apparatusdescribed can be adapted to a wide variety of different applications andthat various changes or modifications may be made therein, each as maybe best suited to the particular application desired and that the scopeof the present invention is intended to include such modifications oradaptations, as defined by the following claims limited only by theprior art.

What is claimed is:

l. A controllable inductor comprising a U-shaped yoke of magneticallypermeable material having two legs with a back portion therebetween, amagnetically saturable core portion bridged across from one leg of saidyoke to the other leg, said magnetically saturable core portion havingan opening therein, a pair of adjustable permeable elements spaced fromeach other and extending from the ends of the two legs of said yoketoward each other, a control winding on the back of said yoke, a signalwinding on said magnetically saturable core portion, said signal windingbeing divided into two halves connected in series aiding relationship,each of said halves passing through said opening and around oppositesides of said magnetically saturable core portion, first adjustmentmeans for regulating the spacing between said elements, and secondadjustment means for changing the spacing between one of said legs andthe magnetically saturable core portion.

2. A controllable inductor comprising a length of magnetically permeablematerial bent into a substantially closed loop with its ends closelyspaced, a control winding on said loop at a position remote from saidends, a magnetically saturable core portion extending across said loopbetween regions on said loop spaced from said ends,

said magnetically saturable core portion having an elongated openingtherein, a signal winding on said magnetically saturable core portion,said signal winding including two connected parts, each part passingthrough said elongated opening and surrounding the respective areas ofsaid magnetically saturable core portion on opposite sides of saidopening, a first adjustment screw of nonmagnetic material extendingbetween said ends for adjusting their spacing, and a second adjustmentscrew for changing the spacing between one of said regions on said loopand said magnetically saturable core portion.

3. A controllable inductor comprising a flexible C- shaped control yokeof magnetically permeable material having a pair of end portions inclosely adjacent relationship, a control winding on said yoke, a signalcore portion of magnetically saturable material having two ends, one ofsaid ends being adjacent to one side of said C-shaped control yoke withthe other end being adjacent to the other side of said C-shaped controlyoke and said signal core portion being bridged across from said oneside of the C-shaped yoke to the other, said signal core portion havingan opening therein, a signal winding on said signal core portion, saidsignal winding including two winding parts each passing through saidopening and around opposite edges of said signal core portion, said twowinding parts being connected in series aiding relationship with respectto magnetic flux in said signal core portion and surrounding saidopening, and adjustment means for adjusting the spacing between the endportions of said yoke.

4. A controllable inductor comprising a flexible control yoke ofmagnetically permeable material having a pair of end portions inoverlapping adjacent relationship, a control Winding on said yoke, asignal core portion of magnetically saturable material having two ends,one of said ends being adjacent to one side of said control yoke withthe other end being adjacent to the other side of said control yoke withthe body of said signal core portion being bridged across from said oneside of the yoke to the other, said signal core portion having anopening therein, a signal winding on said signal core portion, saidsignal winding including two winding parts each passing through saidopening and around opposite edges of said signal core portion, said twowinding parts being connected in series aiding relationship with respectto magnetic flux in said signal core portion and surrounding saidopening, and adjustment means for adjusting the spacing between theoverlapping end portions of said yoke by deflecting the end portions ofsaid control yoke apart.

5. A controllable inductor comprising a control yoke of magneticallypermeable material, a control winding on said yoke, a signal coreportion of magnetically saturable material having two ends, one of saidends being adjacent to one area of said control yoke with the other endbeing adjacent to another area of said control yoke with said signalcore portion extending between said areas of the yoke, said signal coreportion having an opening therein, a signal Winding on said signal coreportion, said signal winding including two winding parts each passingthrough said opening and around opposite edges of said signal coreportion, said two winding parts being connected in series aidingrelationship with respect to magnetic flux in said signal core portionand surrounding said opening, a non-magnetic spacing element between oneend of said signal core portion and the adjacent area of the controlyoke, and an adjusting mechanism for skewing said spacing element,thereby to change the effective length of the reluctance region betweensaid end or" the signal core portion and the control yoke.

6. A controllable inductor as claimed in claim 5 and wherein saidadjusting mechanism is an adjusting screw which tilts said nonmagneticspacing element.

References Cited in the file of this patent UNITED STATES PATENTS349,611 Stanley Sept. 21, 1886 2,462,423 Polydoroff Feb. 22, 19492,488,393 Geiselman Nov. 15, 1949 2,581,202 Post .Tan. 1, 1952 2,771,587Henderson Nov. 20, 1956 FOREIGN PATENTS 1,011,769 France Apr. 9, 1952

